Seal structure for rotary mechanisms



Dec. 9, 1969 c; JONES sRAL STRUCTURE FOR ROTARY MECHANISMS Filed March 8, 1968 4 Sheets-Sheet 1 INVENTOR.

CHARLES JONES v AGENT Dec. 9, 1969 c. JONES 3,482,551

SEAL STRUCTURE FOR ROTARY MECHANISMS 'File'd March a, 1968, 4 Sheets-Sheet 2 FIG. 4

INVENTOR. CHARLES JONES BY 72W 391G120,

. AGENT 1969 c;v JONES 3,482,551

SEAL STRUCTURE FOR ROTARY MECHANISMS Filed March 8, 1968 4 Sheets-Sheet 3 F l G. 7

. INVENTOR.

CHARLES-JONES 72 2W4; AGENT Dec. 9, 1969 c. JONES 3,4 2,551

SEAL STRUCTUREFOR ROTARY MECHANISMS Filed March 8, 1968 4 Sheets-Sheet 4 I INVENTOR. CHARLES .JQNES W 1'? WM AGENT as. IOA

United States Patent O 3,482,551 SEAL STRUCTURE FOR ROTARY MECHANISMS Charles Jones, Hillsdale, N.J., assignor to Curtiss-Wright Corporation, a corporation of Delaware Filed Mar. 8, 1968, Ser. No. 711,783

Int. "Cl. F02b 53/00, 55/00; F04c 17/02 US. Cl. 1238 9 Claims ABSTRACT OF THE DISCLOSURE In a rotary mechanism of the type described, the contact pressure of the apex seals against portions of the housing normally increases at high speeds owing to centrifugal effects, causing wear and power loss through friction. This invention provides a device responsive to centrifugal effects which diminishes contact pressure of the seals.

BACKGROUND OF THE INVENTION This invention relates to rotary mechanisms and is particularly directed to a seal structure for such mechanisms.

Such a rotary mechanism comprises a hollow outer body having spaced end walls interconnected by a peripheral wall to form a cavity therebetween and having an axis along which the end walls are spaced. The inner surface of the peripheral wall defines a multi-lobed profile which, in the form of mechanism described, is basically an epitrochoid. An inner body or rotor is supported for relative rotation within the outer body cavity. The rotor has an axis which is parallel to but laterally spaced from the outer body axis and has end faces disposed adjacent to and in sealing cooperation with the end walls. The outer peripheral surface of the rotor has a plurality of apex portions in sealing cooperation with the adjacent inner surface of the peripheral wall forming a plurality of working chambers therebetween. Each apex portion of the rotor has means for sealing being radially movable and urged into engagement with the peripheral Wall. Patent No. 3,033,180, issued May 8, 1962, discloses sealing means for such a rotary mechanism.

In general, the invention is directed to a rotary engine configuration in which the inner body has a plurality of seals circumferentially spaced about its external periphery. These seals are engageable with the inner surface of the outer body peripheral wall. The centrifugal forces of these seals are variable both in sense and magnitude. In the rotary engine of the above-mentioned patent, the multi-lobed profile of the peripheral wall has alternate concave and convex portions. As more fully explained hereinafter, as the rotor rotates relative to the outer body, the centrifugal forces of each apex seal of the rotor are alternately directed inwardly and outwardly relative to the rotor.

With respect to the outwardly directed centrifugal force, as rotor speeds are increased the force of the apex seal against the peripheral wall increases. Such centrifugal force, if excessive, causes undue frictional wear of the peripheral wall and apex seals, and decreases overall engine efiiciency.

An object of the invention is to provide novel means to compensate for the variable effects of centrifugal forces of the apex seals of the rotor.

A further object of the invention is to provide means to prevent excessive frictional wear of apex seals and the peripheral wall.

Still another object of the invention is to increase the efiiciency of rotary combustion engines.

SUMMARY A rotary combustion engine has a housing defining an internal cavity, the peripheral wall of the housing having a basically epitrochoidal profile as viewed in the axial direction. Disposed in the cavity is a rotor having a plurality of apexes which sweep the peripheral wall in sealing relation, the rotor and the housing defining therebetween a plurality of working chambers which vary in volume on relative rotation of the rotor and housing.

Sealing therebetween is achieved by providing in each rotor apex a slot extending in a direction parallel to the axis, with a seal strip positioned within the slot and spring-loaded to maintain contact with the peripheral wall. In a multi-lobed epitrochoid there are reversals of curvature. In a two-lobed epitrochoid such as that shown in the accompanying drawings, there are two concave curved portions and two convex portions, as viewed from inside the housing. Consequently, as the seal strips trace the epitrochoidal path they are subjected to reversals of centrifugal and centripetal forces, tending to move in the outward direction in the concave portions and inwardly in the convex portions.

The spring loading of the seal strips and the effect of gas pressure in the slots under the seals are sufficient to hold the seal strips in sealing contact while traversing the convex curved portions at low engine speeds, and although there is some centrifugal effect outwardly on the seal in the concave portions, at such low speeds it is relatively unimportant with respect to wear and friction. Good seal ing is required for satisfactory starting and smooth running at low speeds.

However, at high engine speeds, not only is the centrifugally outward effect of the seals in the concave portions greatly increased, with concomitant increase of contact pressure, but also the rubbing speed itself is a cause of increased friction. With such greatly increased friction there is a loss of power, and accelerated wear of the housing and the seal strips. Further, at high engine speeds perfect scaling is no longer required, since gas leakage past the rotor apexes islargely a function of time. Therefore, it would be an advantage to diminish the contact pressure of the seal strips against the peripheral wall at high speeds, or even to relieve it altogether.

The present invention provides in a cavity within each rotor apex an inertia device and lever system linked with the associated seal strip at that apex, and responsive to the same centripetal and centrifugal forces. A weight member and linkage are so arranged that when the centrifugal thrust of the weight is outward the seal strip is retracted inwardly. The weight means is provided with resilient restraining means so that the inertia device does not operate below a preselected engine speed, and exerts increasing effect as the speed increases above the preselected speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section of a rotary engine looking in the axial direction. taken on line 11 of FIG. 2;

FIG. 2 is a cross-section taken on line 2-2 of FIG. 1;

FIGS. 3 and 4 are schematic representations of a body tracing an epitrochoidal path;

FIG. 5 is an enlarged view of one of the rotor apexes of FIG. 1;

FIG. 6 is a view of one of the apex seal strips;

FIG. 7 is a fragmentary view taken within an apex slot of a rotor;

FIG. 8 is a view taken on line 8-8 of FIG. 5;

FIG. 9 is a view similar to FIG. 8 but showing another embodiment; and

FIGS. 10 and 10A are schematics demonstrating the operation of the embodiment of FIG. 9. v

3 DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is illustrated and described in connection with a particular type of rotary internal combustion engine. It will be obvious, however, that the invention is also applicable to other rotary mechanisms and to rotary mechanisms for use as fluid pumps and fluid motors.

Referring first to FIGS. 1 and 2 of the drawing, a rotary internal combustion engine is generally indicated by the reference numeral 10. The engine comprises an outer body 12 having axially-spaced end walls 14 and 16 and a peripheral wall 18 connected therebetween to form a cavity 20. As viewed in a plane transverse to the axis 22 of the cavity (indicated in FIG. 1), the multi-lobed profile of the cavity 20, in the preferred form, is basically an epitrochoid. As illustrated herein, the cavity profile has two lobes. However, as will appear, the invention is not limited to a rotary engine having this specific arrangement.

An inner body or rotor 24 is disposed within the cavity 20 of the outer body 12. The rotor 24 has axially spaced end faces 26 and 28 disposed adjacent to and in sealing cooperation with the end walls 14 and 16. In addition, the rotor 24 has a plurality of circumferentially-spaced apex portions 30 which preferably are one more in number than the number of lobes of the cavity 20. Thus, as illustrated, the cavity 20 has two lobes and rotor 24 has three apex portions 30. The outer periphery of the rotor 24 has a generally triangular profile. The apex portions 30 are in sealing engagement with the inner surface of the peripheral wall 18 to form a plurality of working chambers 32 (three are shown) between the rotor 24 and the outer body 12.

Each working chamber 32 includes a trough or channel 34 in the adjacent peripheral or working face of the rotor 24, for transfer of gases across the cusp of the epitrochoid. The geometrical axis 36 of the rotor 24 is offset from and is disposed parallel to the cavity axis 22.

In the engine 10 illustrated, the outer body 12 is stationary while the rotor 24 is journaled on an eccentric portion 38 of a shaft 40. The axis of the shaft 40 is coaxial with the cavity axis 22. (The cavity axis 22 is hereinafter referred to as the shaft axis.) Upon rotation of the rotor 24, relative to the outer body 12, the working chambers 32 vary in volume. An intake port 42 is provided in the peripheral wall 18 for admitting air and fuel into' the working chambers 32; the intake port may also be located in one or both side walls. A spark plug 44 is provided for igniting the combustion mixture. An exhaust port 46 is provided in the peripheral wall 18 for discharge of exhaust gases from the working chambers 32. As shown in FIG. 1, the rotor 24 turns clockwise in the direction of the arrow 66.

The working chambers 32 have a cycle of operation including the four phases of intake, compression, expansion, and exhaust. The phases are similar to the fourstroke cycle of a reciprocating-type internal combustion engine. It is again emphasized that, although the preferred embodiment disclosed herein is an epitrochoidal rotary engine, the invention is not limited to this specific type of rotary mechanism.

In order to maintain the position of the rotor 24 relative to the outer body 12, an internal ring gear 48 is coaxially secured to the rotor 24. The ring gear 48 is disposed in meshing engagement with a fixed pinion gear 50 secured to the end wall 16. The pinion gear 50 is coaxial with the shaft 40. In the embodiment illustrated, the meshed pinion and ring gears 48 and 50, respectively, have a gear ratio of 2 to 3.

For efiicient engine operation, the working chambers 32 should be sealed. For this purpose a groove or slot 52 extends radially inwardly from each apex of the rotor 24 and runs from one end face 26 to the other end face 28, parallel to the rotor axis 36. An apex seal 54 is in each groove 52 and is in sealing engagement with the inner surface of the peripheral wall 18. As illustrated, each apex seal 54 comprises a. single strip of metal which extends to both end walls 14 and 16 and is in sealing engagement with the peripheral and end walls 18, 14, and 16, respectively. The invention, as disclosed herein, is not limited to this particular type of apex seal structure and may be applied to variations thereof. One such structure is shown in copending application, Ser. No. 575,481, filed July 21, 1966.

Each apex slot 52 has a cylindrically-shaped enlarged portion at each end disposed radially inwardly of its outer edge. Within the enlarged portions are apex seal pins 56 (shown in sectional view of FIG. 2). Each apex seal pin 56 has a slot in register with rotor slot 52 for receiving the radially inner edge of the adjacent end of an apex seal 54.

Each rotor end face 26 and 28 has a plurality of end face seal strips 57 (shown in FIG. 2). Each of these seal strips 57 extends between a pair of adjacent seal pins 56 and cooperates with the apex seal pins 56 to provide a continuous gas seal between the end faces 26 or 28 and the end wall 14 or 16, adjacent thereto. Also, each end face 26 and 28 preferably has an oil seal arrangement 58 (shown in FIG. 2) disposed adjacent to its inner periphery.

The apex seals 54, the apex seal pins 56, and the end face seal strips 57 cooperate to form a continuous seal around each working chamber 32 between the rotor 24 and the outer body 12.

The apex seals 54 are not rigidly retained within the rotor 24. Instead each apex seal 54 is radially movable into and out of its slot 52 in order to maintain contact with the peripheral wall 18 notwithstanding the presence of bearing clearance, thermal distortions, and other inaccuracies. In addition, the seal slot 52 is slightly wider than the seal to permit lateral freedom of the sea]. A suitable spring 60 may be provided in the slot under each apex seal 54 for urging it radially outwardly to insure contact with the peripheral wall 18.

The multi-lobed inner surface of the peripheral wall 18 has circumferentially-spaced concave portions or lobes 62 interconnected by circumferentially-spaced convex surface portions 64. As an apex seal 54 moves along a concave surface portion 62, it tends to move outwardly into contact with the peripheral wall 18. When, however, the apex seal 54 moves along a convex surface portion 64, it tends to move inwardly out of contact with the peripheral wall 18. This tendency to change the direction of the radial movement is a result of changes in the direction of the centripetal and centrifugal forces acting on these apex seals 54. These seal forces are generated as a result of the rotational path each apex seal 54 is forced to travel as a result of being confined in a slot 52 at a rotor apex portion 30. Hence, each apex seal 54 is forced to travel along the epitrochoidal path substantially 'defined by the peripheral wall 18 subject, however, to

limited radial movement as permitted within its apex slot 52.

To more clearly describe the nature of the radial forces acting on the seals, the following discussion is made in connection with the schematic views of FIGS. 3 and 4.

In discussing the effect of forces upon a body, it is customary to consider that body as removed from all surrounding constraints. Each constraint is replaced by a force indicating its effect on that body. The resulting body is known as a free body; the study of forces with respect to that body is known as a free body analysis. It is well known that a free body analysis can be made of a mechanical body. In this manner, a free body analysis can be made, for example, of a rotor or any part carried by the rotor, such as the apex seals. In the following discussion, a free body analysis is made of the apex seals 54 carried by the rotor 24. Primed reference numerals are used in FIGS. 3 and 4 to indicate parts which are similar to parts of the rotary engine of FIGS. 1 and 2.

Newtons First Law of Motion states that: A body at rest remains at rest, and a body in motion continues to move at constant speed along a straight line, unless there is a resultant force acting upon the body.

A body moving in a curved path is accelerated because its velocity is changing continually in direction, even though the body travels at a constant speed. This change is one of direction or sense and not magnitude. Thus, if the path is continually changing in direction, ad ditions are continually being made to it even though the magnitude of the velocity remains the same.

If a body is to proceed from one point to another point on a curved path, maintaining the same magnitude of velocity at both points, an added force will be required. An acceleration is associated with and has the same sense as the added force. The sense of this added velocity and acceleration is toward the center of curvature of the path.

The acceleration toward the center of curvature of the path is called centripetal acceleration. It is well known that force is equal to mass times the acceleration. Thus, a force can be assumed to be acting upon the body; this force is also directed toward the center of curvature and is called centripetal force.

Since for any action there is an equal and opposite reaction (Newtons Third Law of Motion), the moving body exerts an equal and opposite force upon the constraining agent in a direction radially away from the center of curvature. This reaction to the centripetal force is called centrifugal force. Said in other words, when a body moves in a curved path, the force upon that body acting in a direction toward the center of curvature of that path is called centripetal force; the force applied by the body in reaction to the centripetal force, is termed centrifugal force.

There is shown in FIGS. 3 (and 4), a free body 54 (54"), which can be of any shape (shown in the general shape of an apex seal 54), traveling along a curved path from point A toward point G in the direction of arrows 66'. The curved path A-G is in the form of a compound curve (similar to the profile of the peripheral wall 18 shown in FIG. 1) in which the direction of curvature reverses at an inflection point D. The free body 54' is shown in FIG. 3 at four typical positions along this curve A-G, namely at points B, C, E, and F.

An arrow Lb is a straight line tangent to the curved path at point B and indicates the instantaneous direction of travel of the free body 54'. If the free body 54 is to travel along the curved path A-G from point B, rather than in the direction of the arrow Lb, a centripetal force must be applied to it. This force, represented by the arrow Fb, provides the free body 54 with an inward component of motion toward the instantaneous center of curvature of the path at point B.

In the same manner, the arrow L0 is a straight line tangent to the curve and indicates the instantaneous direction of travel of the body 54 at point C. If the free body 54 is to travel along the curved path A-G from point C, rather than in the direction of arrow Lc, a centripetal force must be applied to provide the free body 54' with an inward motion toward the instantaneous center of curvature of the curved path at point C.

Thus, a force directed toward the instantaneous center of curvature must be applied to constrain the free body 54' to follow the curved path A-G instead of following a straight line tangent to the path AD.

Consider now the situation at the point E. Point E is just beyond the point of inflection D on the path A-G. The arrow Le is a straight line tangent to the curve at point E and indicates the instantaneous direction of travel of the free body 54'. Once again, if the free body 54' is to travel along the curved path A-G to G from point E, rather than in the direction of the arrow Le, a centripetal force, represented by the arrow Fe, must be applied. This force Fe provides a component of motion directed inwardly toward the instantaneous center of curvature of the curved path A-G at point B. It should be noted that the curvature of the path A-G reverses beyond the inflection point D. Therefore, the instantaneous centers of the path portion DG are on an opposite side from the instantaneous centers of the portion A-D of the path A-G.

At point F, the situation is substantially the same as at point B. The arrow L1 is a straight line tangent to the curve and indicates the instantaneous direction of travel of the free body 54 at point E. If the free body 54' is to travel along the curved path A-G, rather than in the direction of the arrow L a centripetal force represented by the arrow Lf, must be applied to the body 54' to provide an inward motion toward the instantaneous center of curvature of the curved path at point F.

As the body 54' passes along the path A-G, it tends to travel in a straight line tangent to the curved path at any instantaneous point. In order that the body 54 be constrained to travel along the curved path A-G, a centripetal force must be applied at each instantaneous point. Since, as has been previously explained, the direction of the required centripetal force is always toward the instantaneous center of curvature of the compound curved path A-G of travel of the free body 54', and since the instantaneous centers will be found first on one side and then on the other side of the path A-G, then the direction of the centripetal forces constraining the moving free body 54' must reverse as the body travels past the inflection point D.

As explained above, centrifugal force is a reaction force of a body, equal and opposite to the centrifugal force upon it; therefore, it follows that, if the centripetal force upon the free body 54' reverses direction as the free body 54' travels past the inflection point D, the centrifugal force of that free body 54 must reverse as well.

Both FIGS. 3 and 4 show the compound curve A-G (substantially in the form of a portion of the profile of the epitrochoidal surface of the peripheral wall 18 of FIG. 1). For simplicity in FIG. 4 a seal body 54' (the free body 54' of FIG. 3) is shown only at points C and F. This seal body 54" is illustrated as being within a slot 52' of an apex portion 30 of a rotor 24.

For purposes of the discussion, the apex seals 54" of FIG. 4 are assumed to be being pushed by a side wall 68' of the slot 52' at a constant linear speed along the compound curved surface A-G of a peripheral wall 18'. In common practice, however, the apex seals 54, due to the motion of the rotor 24, will move at varying speeds. Such changes will not vary the sense of the forces being discussed herein. As indicated a'bove with reference to FIG. 3, the sense of the cenrtipetal forces will be directed toward the instantaneous center of curvature. For example, at point C, in the absence of a peripheral wall 18' of an outer body (and neglecting friction between the seal body 54" and the walls of the slot 52), the seal body 54", pushed by the rotor 24', would travel in a straight line in the direction of the arrow Lc. The peripheral wall 18', however, prevents the seal body 54" from traveling in such a direction. The wall 18' forces or constrains the seal body 54" to travel along the curved path A-G. Thus, at point C, as well as at each instantaneous point along the portion of the curved path A-D, the centripetal forces of the peripheral wall 18' constrain the seal body 54". The equal and opposite centrifugal forces to the centripetal force is shown in FIG. 4 by the arrow F'c.

Similarly, at point F the seal body 54", in the absence of a centripetal force, would travel along a straight line in the direction of the arrow Lf. As shown in FIG. 3, a centripetal force at point P (arrow Ff shown in FIG. 3) is directed toward the instantaneous center of curvature 7 and outwardly relative to the rotor axis 36 and shaft axis 22 (shown in FIG. 1).

The peripheral wall 18 cannot provide an outward centripetal force on the seal body 54". To provide the outward centripetal force, a spring 60 (which can be assumed to include the effect of any gas pressure) is provided between the seal body 54 and the bottom wall 70' with the side walls of the groove 52. The spring 60' is designed to exert an outward force (arrow Fs) on the seal body 54" which is sufficient in magnitude to provide the centripetal force necessary to force the seal to travel along the convex paths at the point F and in the addition to insure adequate contact pressure between the seal body 54" and the peripheral wall 18 in all positions of the seal body 54 along its path of travel.

Neglecting any friction between the seal body 54" and the side wall 68' of the slot 52', the contact pressure at point P is equal to the difference between the force Fs, exerted by the spring 60 on the seal body 54", and the centrifugal reaction force occurring at point F. This relationship will hold at each point along the convex portion 64' of the peripheral wall 18. At every other point, such as the concave portion 62 of the peripheral wall 18', however, the spring force and the centrifugal force (arrows Fs and F'c, respectively) will both act in the same direction, urging the seal against the epitrochoidal inner surface 18'.

The contact pressure force of the seal body 54" against the curved surface A-G of the peripheral wall 18 at point C is equal to the sum of the spring force Fs and the centrifugal force Fc. Therefore, along the concave portions 62' the seal contact pressure against the peripheral wall 18' is greater than the contact pressure at the convex portions 64'. Accordingly, if .the contact pressure of the seal member 54" is adequate at a point on the convex portion 64', such as at point P, it may become excessive at points on the concave portion 62, such as point C.

Gas leakage past seals is a function of time. As the rotational rate increases, there is less time for gases to escape from the working chambers. Therefore, as the rate of rotation is increased, the necessity for close-sealing engagement between the apex seals 54 and the peripheral wall 18 diminishes. Sealing contact, useful at low speeds, will introduce at high speeds undesirable housing and seal wear and increase a loss of power due to friction.

This invention overcomes these limitations by providing inertia devices responsive to the same centrifugal and centripetal forces to which the seal strips are subject, and so constructed as to exert a restraining force on the seals to reduce contact pressure. In FIGS. and 8 there is shown a weight and lever system disposed within a cavity at each apex portion of the hollow rotor, and linked to the seal strips in such a manner that when the weight thrusts centrifugally outward the levers spread and by a camming action pull the seal inwardly within its slot.

A seal strip 54 is disposed within each seal slot 52, the seal strip having a pair of elongated cam apertures 72 therethrough (best shown in FIG. 6). Each cam aperture is positioned toward one of the ends of the seal strip, and is an elongated slit having its axis disposed at an angle to the length of the seal. The angle shown is 45, but any other angle which will produce the appropriate degree of radial movement may be selected.

The seal slot 52 has in each side wall thereof a pair of recesses 74 which are continued through the bottom of the slot to communicate with the interior cavity at the apex of the rotor (best shown in FIG. 7). In each of the receses 74 at its upper end there is an elongated cam track 76 or keyway extending more deeply into the seal slot wall than the recess 74, and having the same general form as the cam aperture 72 but with its axis parallel with the axial dimesion of the seal strip. A lever 78 is positioned within each of the recesses 74 with one end extending inwardly into the rotor cavity at an angle of approximately 45. One of the levers is provided at its inner end with a clevis 80 in which is nested the inner end of the other lever, the two inner ends being pivotally joined by a pin 82 or other convenient member. Also mounted on the pin 82 is a pair of weights 84, one on each side of the inner ends of the levers.

The upper end of each lever is provided with a clevis 86 having a transverse bore therethrough, with the clevis spanning the radially inner edge or bottom of the seal strip 54. In each bore is disposed a camming pin 88 extending through the cam aperture 72 of the seal strip .and having its ends seated in the cam track 76. Within the rotor cavity the two levers are linked together by a tension spring 90.

It will be apparent that when the engine is in operation, there will be a centrifugally outward thrust of the weights 84 while their associated rotor apex is traversing the concave portion of the peripheral wall. When the outward thrust of the weights is great enough to overcome the tension of spring 90 the weights will move in a radially outward direction, pushing the inner ends of the levers also in the same direction and exerting a spreading action on the upper ends of the levers. Since the pins 88 are restrained from radial movement by their engagement with the keyways 76, they ride in the axial direction in the keyways as the lever arms spread. Since pins 88 are also engaged with the cam apertures or slits 72 through the seal, and since these slits are angularly disposed with respect to cam tracks 76, the seal is pulled radially inwardly in proportion to the spreading of the levers, which in turn is proportional to the radially outward thrust of the weights.

The tension of spring 90 is selected for any desired engine speed, so that below the preselected speed the inertia device will not operate, at transitional speeds the levers will exert only a small inward pull on the seal and reduce the contact pressure, and at higher speeds they will spread suificiently to retract the seal from contact with the peripheral wall. The actual seal movement in the radially inward direction to remove it from contact with the peripheral wall is quite small, only a few thousandths of an inch, and the length of the cam slits therethrough and of the cam tracks in the rotor has been exaggerated in the drawings for clarity of illustration. Also, the cam slits need not be pierced at 45 to the axial dimension of the seals, and the cam tracks need not be parallel with the axial dimension of the rotor. It is only necessary that the cam slits and cam tracks be disposed at different angles, with the axially outward ends of the cam slits being radially further out than the ends of the cam tracks; the degree of disparity of the angles will govern the amount of retraction of the seals for a given amount of movement of the camming pins in the axial direction.

FIG. 9 shows a related form of inertia device producing the same result in response to the same forces. The same seal strip 54 having the same form of cam slits 72 is used. However, in this embodiment the levers 78a move only in the radial direction and extend through appropriate radially disposed recesses communicating between the seal slot and the rotor cavity, such recesses being disposed one adjacent to each axial end of the rotor, and each recess is continued into the rotor cavity by a tubular guide member 92 which serves to constrain the lever to straight-line radial movement. The inner end of each lever is surrounded by a compression spring 90a having a strength selected, as in the previous embodiment, so that the inertia device will not operate below a predetermined engine speed, will operate minimally at transition speeds, and fully at high speeds. The radially inner ends of the levers are joined by a weight 84a which provides the centrifugally outward thrust.

The cam tracks or keyways 7611 provided in the wall of the seal slot of the rotor are in this embodiment disposed at an angle, rather than horizontal, but at a lesser angle than that of the cam slits 72 through the seal. As shown, the cam tracks are at 30 from the horizontal. The bores 92 through the clevises 86 of the levers are elongated in the horizontal direction, so that the camming pins 88 may move axially outwardly as they follow the cam tracks, since the levers have only radial movement.

FIGS. and 10A are diagrams showing schematically the three elements engaging the camming pins, in much exaggerated length for clarity of illustration. The cam slits 72 in the seal are shown at 45, cam tracks 76a at 30, and elongated bores 92 horizontal. FIG. 10 shows the elements as if in rest position, and FIG. 10A shows a'moved position, wherein the lever has moved upward, the camming pin 88 has therefore moved upward and axially outward, along the keyway 76a, and the seal has been cammed downward. The small arrows on the centerlines of the elements show the directions of movement in FIG. 10A.

Again in this embodiment, it is not necessary that the angles of the cam slits in the seals and the keyways in the rotor be those shown. It is only necessary that the disparity of angles be such that the seal will be drawn radially inwardly as the camming pins move in the axially outward direction in response to thrust by the inertia device.

What is claimed is: 1. In a rotary combustion engine of the type having an outer body defining an internal cavity having a central axis, the outer body having a peripheral wall with an inner surface of basically epitrochoidal profile having a plurality of inwardly concave and convex portions, a rotor mounted within the cavity for rotation with respect to the outer body on a rotor axis planetating about the central axis, the rotor having a plurality of apex portions, the profiles of the rotor and of the peripheral wall defining therebetween a plurality of variable-volume working chambers, each of the apex portions having an axiallyextending slot with a radially movable seal strip positioned therein for sealing against the peripheral wall, means for reducing the contact pressure of the seal strip against the peripheral wall comprising:

(a) inertia means carried by the rotor for restraining radially outward movement of the seal strips while traversing the concave portions of the peripheral wall, including,

(i) weight means responsive to forces acting generally radially with respect to the rotor axis, (ii) linking means extending between the weight means and the seal strip, and

(iii) the rotor, the seal strip, and the linking means being mutually engaged in a cooperating relationship providing camming means to exert radially inward pull on the seal strip when the weight means exerts radially outward thrust on the linking means.

2. The combination recited in claim 1, wherein the linking means includes at least one lever arm bearing the weight means at its radially inner end, the camming means includes a camming pin borne by the lever arm at its radially outer end, the rotor has a keyway in at least one side of the seal slot, and the seal strip has at least one cam slit therethrough, the camming pin engaging the cam slit in the seal strip and being translatable along the keyway, the keyway and the cam slit being angularly disposed to each other in such a manner that when the camming pin is translated along the keyway it exerts a camming action on the cam slit to move the seal strip in the radial direction.

3. The combination recited in claim 2, wherein there are two lever arms pivotally joined at their radially inward ends, their other ends extending in the general radial direction at an angle to each other, a camming pin borne by each lever arm at its radially outward end and enga'ge'd with a cam slit in the seal and with a keyway in the rotor in such a manner that when the centrifugal thrust of the weight means is in the radially outward direction the outward ends of the lever arms spread angularly apart and exert a camming action on the cam slits to move the seal strip in a radially inward direction.

4. The combination recited in claim 3, wherein a tension spring is connected at opposite ends to each of the two lever arms and resiliently urging them toward each other, the spring force of the tension spring being preselected so that the weight means will be ineffective to spread the outward ends of the arms below a predetermined engine speed.

5. The combination recited in claim 4, wherein the rotor has an interior cavity at the apex portion, there is passage means communicating between the cavity and the seal slot, the lever arms have their pivotally joined radially inner ends and the weight means positioned within the cavity, and their radially outer ends extend through the passage means into the seal slot.

6. The combination recited in claim 5, wherein there is an inertia device at each of the rotor apexes linked with the associated seal strip at that apex.

7. The combination recited in claim 2, wherein the linking means includes a pair of lever arms keyed for straight-line radial motion and bearing the weight means at their radially inner ends, the radially outer end of each lever arm bearing the camming pin in an elongated bore allowing translation therealong.

8. The combination recited in claim 7, wherein each of the lever arms has spring means biasing it radially inwardly, the spring force of the spring means being preselected so that the weight means will be ineffective to thrust the lever arms radially outwardly below a preselected engine speed.

9. The combination recited in claim 8, where there is an inertia device at each of the rotor apexes linked with the associated seal strip at that apex.

References Cited UNITED STATES PATENTS CORNELIUS J. HUSAR, Primary Examiner US. Cl. X.R. 230 

